Alkaloids and other Nitrogen containing compoundsDominador T. Callo Jr.

What is Alkaloid?

Alkaloids are a group of naturally occurring chemical compounds that contain mostly basic nitrogen atoms.

Alkaloids are produced by a large variety of organisms, including bacteria, fungi, plants, and animals, and are part of the group of natural products (also called secondary metabolites).

History Alkaloid-containing plants have been used by

humans since ancient times for therapeutic and recreational purposes. For example, medicinal plants have been known in the Mesopotamia at least around 2000 BC.

Extracts from plants containing toxic alkaloids, such as aconitine and tubocurarine, were used since antiquity for poisoning arrows.

Studies of alkaloids began in the 19th century. In 1804, the German chemist Friedrich Sertürner isolated from opium a "soporific principle" (Latin: principium somniferum), which he called "morphium" in honor of Morpheus, the Greek god of dreams; in German and some other Central-European languages, this is still the name of the drug. The term "morphine", used in English and French, was given by the French physicist Joseph Louis Gay-Lussac).

A significant contribution to the chemistry of alkaloids in the early years of its development was made by the French researchers Pierre Joseph Pelletier and Joseph Bienaimé Caventou, who discovered quinine (1820) and strychnine (1818). Several other alkaloids were discovered around that time, including xanthine (1817), atropine (1819), caffeine (1820), coniine (1827), nicotine (1828), colchicine(1833), sparteine (1851), and cocaine (1860).

Classification More recent classifications are based on

similarity of the carbon skeleton (e.g., indole-, isoquinoline-, and pyridine-like) or biogenetic precursor (ornithine, lysine, tyrosine tryptophan, etc.). However, they require compromises in borderline cases; for example, nicotine contains a pyridine fragment from nicotinamide and pyrrolidine part from ornithine and therefore can be assigned to both classes.

Alkaloids are often divided into the following major groups: "True alkaloids“- it contains nitrogen in

the heterocycle and originate from amino acids.Their characteristic examples are atropine, nicotine, and morphine. This group also includes some alkaloids that besides nitrogen heterocycle contain terpene (e.g., evonine) or peptide fragments (e.g. ergotamine). This group also includes piperidine alkaloids coniine andconiceine although they do not originate from amino acids.

"Protoalkaloids“ - it contains nitrogen and also originate from amino acids. Examples include mescaline, adrenaline and ephedrine.

Polyamine alkaloids – derivatives of putrescine, spermidine, and spermine.

Peptide and cyclopeptide alkaloids.

Pseudalkaloids – alkaloid-like compounds that do not originate from amino acids. This group includes, terpene-like and steroid-like alkaloids, as well as purine-like alkaloids such as caffeine,  theobromine and theophylline. Some authors classify as pseudoalkaloids such compounds such as ephedrine andcathinone. Those originate from the amino acid phenylalanine, but acquire their nitrogen atom not from the amino acid but through transamination.

Main classes of monomeric alkaloids

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